This invention relates to a digitizer in which electrostatic coupling between patterned electrodes of a digitizer tablet and a cursor or stylus movable thereon creates signals indicative of the position of the cursor on the tablet.
Devices which are the general subject of this invention are commonly referred to as "digitizers." The earliest digitizers were mechanical devices with restrained arms. Later digitizers have free-moving cursors, and use various forms of coupling phenomenon between a cursor and a digitizing tablet, such as electromagnetic, electrostatic, and even sound coupling. Signals in the tablet have been handled by means of magnetostrictive principles, resistive surfaces, or other conductors, but generally these devices depend upon monitoring of signals introduced in a plurality of X and Y conductors or a resistive film. Since signals from each of the conductors need to be processed individually, or signals from several points on the periphery of a resistive layer, the complexity and cost of this type of digitizer, including its electronics, is high. Thus, there is a need for an improved digitizer.